The National Institute on Alcohol Abuse and Alcoholism (NIAAA) seeks to expand research applying genetic epidemiologic methods to studies of alcohol and other substance use disorders (AUD/SUD; alcohol or drug abuse and dependence). Previous studies using twin, adoption, and family approaches indicate that genetic factors substantially contribute to the vulnerability to AUD/SUD. Shared environmental factors have also been shown to strongly influence risk; however, the influence of genetic factors appears to increase with age. Significant advances also have been made in our understanding of the onset and progression of AUD/SUD and in defining a disinhibited phenotype. Building on these findings, new studies are needed to apply genetic epidemiology approaches to advance our understanding in a variety of areas, integrate as well as differentiate genetic and environmental factors in the onset and maintenance of AUD/SUD; broaden and refine phenotypic definitions of AUD/SUD; guide the translation of etiologic findings to prevention, treatment, and gene identification, and meet the methodologic challenges of the field. A variety of research approaches have established that AUD/SUD are heritable complex disorders, and that family history of AUD/SUD is probably the most potent risk factor for these disorders. Heritability estimates have been high, and shared environmental effects appear to be strong. Genetic epidemiologic studies have highlighted the nature of AUD/SUD as a developmental disorder, particularly as part of a general vulnerability to problem behavior associated with disinhibition. A surprising degree of non-specificity has been found in regard to choice of substance and gender; that is, many risk factors appear to operate similarly in the vulnerability to abuse and dependence for a variety of drugs in men and women. Increasingly sophisticated approaches have also been applied to understand the high prevalence of psychiatric comorbidity with AUD/SUD. Important findings are emerging on the roles of gene-environment correlation and gene-environment interaction in elucidating the development of substance and alcohol use and AUD/SUD. The purpose of this project is to conduct a cross-sectional, nationally representative survey of the U.S. general population, 18 years or older, that will collect phenotypic information (questionnaire) on alcohol and drug use and disorders, co-occurring psychiatric disorders, and medical disorders related to AUD/SUD as well as background information and risk factors for the aforementioned disorders. DNA will also be collected.